Air preheating construction for furnaces



Sept. 6, 1932. H. A. ATWATER AIR PREHEATING CONSTRUCTION FOR FURNACESFiled July 10, 1929 2 Sheets-Sheet 1 IN V EN TOR:

ATTORNEY P 6, 1932- H. A. ATWATER AIR PREHEATING CONSTRUCTION FORFURNACES Filed July 10, 1929 2 Sheets-Sheet 1N VENTOR:

A TTORNEY Patented Sept. 6, 1932 nanny a. mwarna. or? CITY; M SSo-Iml.it

AIR. BBEHIJATInG. cons'mncrron ron runnnonsf Application flied my 10,1925, Serial 116,377,263.-

This invention relates tofurnace construe-H tion, and aims to provideimproved features in, thearrangement and construction of" the passagesthrough which the airis conducted to the combustion chamber, with a viewto effectinga'more uniform andiefiicl'ent pro-heat ingof the airrequiredfor furnaces.

Accordingly, the invention comprises an air pre-heating constructlonhavlngprovislon for sub-dividing the air flow into more-orlessseparateor independent currents,by'means of'a partition structurewhich serves notonly to split up, the incoming air into a plurality ofstreams allflowing in the same direction, butalso to subject the air toextensive pre-heating areas which are maintained heated by conductionfromthefio'or of the combustion chamber. The invention further comprisesa pre-,

heating structure which is economicaland:

comparatively easy'to assemble and adapted to maintain its, structuralposition and shape Without material? variation due to temperaturechanges.

With the foregoing general objectsin view, the invention will now bedescribed'by reference to the accompanying drawings illustrating onetypeof construction which I have devised forembodying the, improvements inpractical form, after which the various feag tures andcombinationsdeemed to'be'novel will be particularly set forth andclaimed.

In, the drawings I Figure 1 is a horizontal sectional view showing afurnace structure embodying the present improvements, and representing asection taken'on the line II of Figure 2, with portions broken away;Figure 2 is a vertical transverse sectional view, representing a sectiontaken on the line IIII of Figure 1 1 Figure 3 is a vertical longitudinalsectional view, representing a section taken on the line III-1110fFigure 1 ,and i Figure '4. .is a perspective View, on a larger scale,illustrating one of the units of the partition structure two adjoiningfloor sections prior to their assembly.

The invention as illustrated by the draw.- ings involves variousfeatures of improve.-

ments roverfthe "furnace construction covered; by Letters PatentiNo.1,573,507granted tor- 6; on Feb. 16, 1926, while retaining all-of the,vantageous featuresof the patent.- As illus: tratedin the patent, theincomingair was in: tercep ted= by vertical transverse partitions havingopenings. operatingto split up .theaifrs flowinto a plurality of minorstreams all-gmov-u V ing in the same direction, but certain disad-jvantages of j this construction; lay in the pal-1.. tial' obstruction ofthe air flow-due tothe. area. of; the partitions, anduin the factthatithe greater portion of the heating: effect wasde,

, pendent upon the-action o'f' the steel cover or floor-plates formingthe roof pre-iheating passages;

While various expedients or ceiling of the I might;

1 resortedito. for increasing the rate of he'at transfer fromv thecombustion chamben for pre-heating the air, most of thesefare' foundtooiferyarious objections, such asjobstructingthe air-flow by cuttingdown. the crosssectional area of the air passage and; hence,

the feeding capacity thereof, such as would; be the result of anytransverse partition structure; likewise, the friction introduced bysuch type of structure; the dirt and refuse j collectingtendency of anyavailable horizontal partitioning elements that might be used, which ischaracteristic of tube assent" bli'es often employed forheatingefi'ects, whereas such tube elements also interpose an excessivedegree of friction, retardingthe flow and reducing the capacity withcorresponding draft losses; and further, the difliculty ofsatisfactorily andeffic-iently support-i ing such assemblies' at allnecessary points! without bucklingoran'y malformation of'the steel partscomposing the jn. H 1 The present construction, therefore, aims toovercome these various objections by providing a parti tioning andpreheating means with as full a preheating efi'ect as possible and withminimum'red-uction of the capacity of the air feed passages. .i 1

Referring now tofthe drawings. in detail, these show .a furnacestructure comprising: sidewalls 10 and end walls 11 of anypracti:

cal type for providing a furnacecornbustion chamber '12. The floor ofthis chamber cona and the tiling comprising the floor struc:

ture.

I As in the patent referred to, this arrange-- ment provides a floorconstruction which readily transmits heat fromthe chamber 12 to thespace beneath the floor for pre-heat ing the air on its way to saidchamber, and at'the same time affords a liquidtight floor- 3 ing toprevent any liquid fuel (where such fuel is used) from leaking through,and the slope of the floor promotes proper drainage of any excess orunburnt fuel from the combustion chamber. For such drainage, a channelor trough isprovided surrounding the air feed opening'22 through thefloor beneath the burner compartment 23 formed by the arch 24, andleading to an outlet pipe 26..

For pre-heating the air supplied the combustion chamber, the spacebeneath the floor" of said chamber is partitioned to form air-.

feed passages similarly arranged at the opposite sides of the middlelongitudinal line of the furnace, the partitioning structure including'longitudinal metal sheets or plates suitably positioned and secured forforming intake passages 31 communicating at their frontends with the airintake openings 32 (provided in the front wall 11 of the furnace.

structure) and at their rear ends with a transverse passage- 33, fromwhich a return pre-heating passage34 is formed between said partitionsheets or plates 30 leading to the floor opening 34, through which theair is discharged into the burner compartment 23.

By this means, the incoming air is caused to pursue acourse, asindicated by the arrows in Figure 1, from {the openings 32, through thepassages 31, 33 and 34, during which course the air is subjected to thepre-' heating effect of successively and increasingly hotter portions ofthe bottom face of the fur-' nace'combustion chamber, as explained in myprevious patent referred to. I V y .In order to further subdivide orsplit up the incoming air and to promote the preheating action, verticalsheets'36 having a combined pre-heating and partitioning function,

are arranged in longitudinal and spaced relation within the passages 31and 34, the upper margins of these sheets 36 being formed with rolledflanges 37 adapted to be interengaged between the tongue and grooveflanges 16, 17, of the cover sheets or plates '15, as clearlyrepresented in Figures 2 and 4. I The lower edges of the sheets 36 areformed with lateral stiffening flanges 38 for which spaced notches 40are provided in transverse angle member 41 extending across the lowerportions of the passages 31 and 34, as shown in Figures 1 and 2. Inorderto facilitate the assembly of the vertical sheets 36, their uppermargins are cut away sufiiciently, as indicated at 42, to clear theupper transverse angles 18 and permit insertion of the sheets 36 intoengaged relation with the flanges 16 of the cover sheets 15, and thendropping of the sheets 36to seat their bottom flanged portions 38 intothenotches 40 of the angle members 41 comprising the underframe. Thusthe liquid tight character, of the joints between the cover sheets 15 ispreserved by this method of mounting and attachingthe partition sheets36, the latter serving to divide the space within each of said passages31 and 34 into a plurality of separate longitudinal and relatively smallpassages with a minimum of obstruction tothe air flow, and accordingly,increased area of pre-heating surface. An extended intimate contact ismade be tween the hot cover sheets and the partitioning sheets, wherebythe conduction ofheat throughout the latter is promoted. In this 7connection, it may also be noted that the type of oint or seamconnecting the sheets 15 and 36, retains all the structural stiffness ofthe channel shape design ;while permitting all necessary compensatingaction due to tem, perature changes, the only fastenings employed'beingat the front ends'of the sheets 15 where bolts '45 are used for securingsaid ends to rigid frame pieces 46 provided with the slots 47 for saidbolts (see Figure 1).

A pre-heater construction is thus provided which not only preserves alltheadvantages of my previous construction, such as temperaturecompensating, leakeproof and air-tight joints, and efficient drainage,but important new advantages are secured in the way of more efficientpre-heating action. It isfound that the provision of series oflongitudinal partitionsheets brings about the desired effect of bothsplitting up the flow of air into a multiplicity of thin streams orcurrents of air and of spreading these streams of air over a maximumheating surface as presented by both sides of the partitions orpre-heating sheets, in which a maximum flow of heat by conduction hasbeen established by Virtue of their intimate connection throughout theirupper margins with the seams between the utilized as far as possible,with the minimum frictional resistance tothe movement of the air, andhence with a minimum of draft loss through the preheater. The collectionof dirt and refuse which characterizes horizontal or tube structures isalso obviated, and practically no attention is required for lreeping theimproved construction clear and clean in all respects.

The type of construction, in addition to its being free to compensateautomatically for temperature changes, is also protected againstbuckling or warping tendencies, by virtue of the oint structure in theseam connections and the reinforcing flanges at the bottom margins ofthe pro-heating sheets.

l Vhile I have herein illustrated and described what I have found toconstitute one practical and efficient form of construction forembodying the proposed improvements, I desire to be understood asexpressly reserving the right to make all such changes or modificationsas may fairly fall within the scope of the following claims.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. A furnace construction comprising a combustion chamber having afloor, and an airfeed passage beneath said floor for conducting air fromthe exterior of ti e furnace to said chamber, and one or more metallicair pre-heatin sheet-s suspended from said floor in position tosubdivide the flow of air through said passage and subject the same tothe preieating effects of the lateral faces of said sheets.

2. A furnace construction comprising a combustion chamber having afloor, and an air-feed passage beneath said floor for conducting airfrom the exterior of the furnace to said chamber, and one or moremetallic air pre-heating sheets freely suspended from said floor inlongitudinal position within said passage for subdividing the flow ofair therein and subjecting the same to the preheating efi'ect of thelateral faces of said sheets.

3. A furnace construction comprising acombustion chamber having a floor,and an air-feed assage beneath said floor for con- I 'rom the exteriorof the furnace to said chamber, said floor inclu I a metallic coverplate structure overlyir said passage, and one or more metallic airrare-heat ing sheets suspended from said structure in position tosubdivid theflow of air through said passage and subject the same to thepreheating effect of the lateral faces of said sheets.

4. A furnace construction comprising a combustion chamber having afloor, an airfeed passage beneath said floor for conducting air from theexterior of the furnace to said chamber, said floor including a metalliccover plate structure overlying said passage, and one or more metallicair pro-heating sheets suspended from said structure in position tosubdivid the flow of air through said passage and subject the same tothe preheating effect of the lateral faces of said sheets, said platestructure audpre-heating sheets being-connected and arranged forautomatic compensating action in response to temperature changestherein.

5. A furnace construction comprising a combustion chamber having afloor, an airfeed passage beneath said floor for conducting air from theexterior of the furnace to said chamber, said floor including asectional metallic cover plate structure overlying said passage, and oneor more metallic air preheating sheets interengaging said cover platestructure at the connecting lines of the sections thereof and suspendedwithin said passage in position to subdivide the flow of air therein andsubject the same to the pre-heating effect of the lateral faces of thesheets.

6. A furnace construction comprising a combustion chamber having afloor, an airfeed passage beneath said floor for conducting air from theexterior of the furnace to said chamber, said floor including asectional metallic cover plate structure overlying said passage, and oneor more metallic air preheating sheets suspended longitudinally Withinsaid passage in position to subdivide the flow of air therein andsubject the same. to the pre-heating effect of the'lateral faces of thesheets, the upper margins of said sheets and the connected portions ofsaid cover plate sections being formed with interengaging tongue andgroove flanges providing liquid and air-tight seams along saidconnecting lines.

7 A furnace construction comprising a combustion chamber having a floor,an airfeed passage beneath said floor for conductinn" air from theexterior of the furnace to said chamber, said floor including a metalliccover plate structure overlying said passage, one or more metallic airpie-heating sheets suspended from said structure in position tosubdivide the flow of air through said passa ge and subject the same tothe pre-heating effect of the lateral faces of said sheets, and meansreinforcing the lower margins of said sheets against lateral warping orbuckling while permitting longitudinal expansion or contraction of thesheets in response to temperature changes.

In witness whereof I hereunto afiix my signature. 7

HARRY A. ATWATER.

